The objective of the investigations proposed is tat of quantitatively characterizing by means of direct measurements, th transport properties of in-vivo &in-situ of solid tumor microcirculation. The work proposed includes the implemtation of a biological tumor sandwich window preparation which can be studied by existing and available microcurculatory methods, using the BL-DMBA #1 mammary adenocarcinoma tumor in F344 rats which is well characterized in terms of histology, growth rate and radiation sensitivity. The expertise developed in this area will be subsequently utilized to develop a nude mice mammary carcinoma sandwich preparation, which will be studied by the same methods.